1. Field of the Invention
The present invention relates to an electrostatic ink-jet recording apparatus in which charged particulate material in ink is deposited on a recording medium with the action of electrostatic force for recording, and, more particularly, to an electrostatic ink-jet recording apparatus which enables it to simplify its manufacturing process.
2. Description of the Prior Art
Conventionally, as described in PCT Publication Number WO 93/11866, an electrostatic ink-jet recording apparatus has an electrostatic ink-jet recording head, and an opposite electrode positioned behind recording paper and for producing an electric field between the recording paper and the ink-jet recording head. The ink-jet recording head has, as shown in FIG. 1, a head body 40, and ink channels 41 and 42 formed within the head body 40 and through which ink liquid supplied from an ink tank or the like flows. The ink channel 41 supplies the ink to the front end of the head body 40. The ink liquid supplied to the front end is then introduced into the ink channel 42 along an ink director 43. This forms a circulating path of ink liquid.
A plurality of ejection electrodes 45 and insulators 48 are alternately formed on the inclined surface of the head body 40. Each ejection electrode 45 is driven by each of drive sources 49 when ejecting the ink. Each of the front end 46 of the ejection electrode 45 is formed with a blade 47 projecting from the end of the ink channel 41 and projects therefrom. The blade 47 projects in the direction of ink ejection, and is necessary for directing the front end 46 toward the direction of ink ejection. This makes parallel the direction of ink ejection and the direction of the front end 46 of the ejection electrode. The front end 46 of the ejection electrode faces an opposite electrode (not shown). Although it does not describe how to form the ejection electrode, it is anticipated that it is formed by laminating conductors. The ink liquid in the ink channel 41 is supplied to the front end 46 of the ejection electrode by its surface tension. This forms an ink meniscus at the front end 46.
The ink liquid contains a charged particulate material for coloring. Hereinafter, the charged particulate material is called a toner particle (or toner particles). While the toner particles are positively charged by zeta potential, the ink liquid maintains to be electrically neutral in a state where no voltage is applied to the ejection electrode 45. The polarity of zeta potential depends on the characteristics of the toner particle.
When a positive voltage is applied to the ejection electrode 45, positive potential increases in the ink liquid. At the moment, the toner particles move in the ink liquid toward the front end 46 of the ejection electrode 45 by an electric field acting between the ejection electrode 45 and the opposite electrode (not shown). When the toner particles reach the front end 46, they are strongly attracted toward the opposite electrode by an electric field acting between the front end 46 and the opposite electrode. When Coulomb force acting between the toner particles concentrated at the front end 46 of the ejection electrode and the opposite electrode significantly exceeds the surface tension of the ink liquid, agglomerations of toner particles accompanying small amount of the ink liquid fly from the front end position of the ejection electrode toward the opposite electrode, and deposit on the surface of a recording medium. Thus, aggregations of charged particulate material flies one after another from the front end of the ejection electrode by applying voltage to the ejection electrode, thereby printing being performed.
The conventional ink-jet recording head shown in FIG. 1 should orient the front end 46 of the ejection electrode 45 so that the ink is ejected in the predetermined direction. Thus, the blade 47 for the orientation should be formed on the end of the ink channel 41. However, the ink must move under the blade 47 in order that the ink from the ink channel 41 reaches the front end of the ejection electrode 45. This extends the distance for the ink liquid and the toner particles therein to reach the front end 46, so that ejection of the ink becomes unstable. In addition, the extended distance calls for the drive source 49 to apply a very high voltage to the election electrode. Higher pulse voltage applied to the ejection electrode causes a problem making difficult fabrication of a driver. Further, there arises a problem that, when pulse driving is performed at a high voltage, noise may be induced in peripheral electronics, leading to malfunction.
In addition, since the ink circulating path of the ink channels 41 and 42 is separated from a point for ejecting the ink or the front end 46 of the ejection electrode, many of toner particles in the ink channel 41 fail to reach the front end 46, but return to the ink channel 42 through the director 43, so that a sufficiently dense image cannot be recorded.